import java.util.*;
/*
public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution12 {
    public ListNode FindFirstCommonNode(ListNode pHead1, ListNode pHead2) {
        if(pHead1 == null || pHead2 == null) {
            return null;
        }
        ListNode p1 = pHead1;
        ListNode p2 = pHead2;
        while(p1 != p2) {
            if(p1 == null) {
                p1 = pHead2;
                continue;
            }
            if(p2 == null) {
                p2 = pHead1;
                continue;
            }
            
            p1 = p1.next;
            p2 = p2.next;
        }
        return p1;
    }
}
